Thermoelement

Abstract

A thermoelement (1) for measuring the temperature in gaseous or fluid media by means of one or more thermocouples (4) comprising wires of different metals welded together which give off a resulting electrical voltage when heated and are configured as a measuring insert (2) arranged in an insulating rod (3) disposed in a heat-resistant protective tube (11) that can be connected to a connection head (6), the protective tube being wholly or partially surrounded by a holding tube (21). To prevent a high input of heat which has an unfavourable effect on a temperature measurement, the holding tube (21) is supported against the protective tube (11) at a radial distance from the protective tube (11), and a heat-resistant trace (31) and optionally an insulating material (33) are inserted between the protective tube (11) and the holding tube (21), and the holding tube (21) is attached to the connection head (6) and / or the protective tube (11) in one or both end areas and is provided with thermal insulation.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a thermoelement for measuring the temperature in gaseous or fluid media by means of one or more thermocouples, each comprising wires of different metals welded together, which give off a resulting electrical voltage when heated, and are configured as a measuring insert arranged in an insulating rod inserted in a heat-resistant protective tube that can be connected to a connection head, in which case the protective tube is wholly or partially surrounded by a holding tube.[0003]2. Description of the Prior Art[0004]Thermoelements of this kind are familiar in numerous different embodiments and have proven effective in practice for measuring the temperature in thermal process systems. Although the protective tube and / or also the holding tube are manufactured from more or less heat-resistant materials, according to the particular application, the heat input into the contact surfaces of the pro...

AI Technical Summary

Benefits of technology

[0005]It is therefore the object of the present invention to provide a thermocouple of the aforementioned type in which a high input of heat, which has an unfavourable effect on the temperature measurement, is avoided. Instead, it is attended to ensure that the connection head is insulated against heat to a large extent, so that incorrect temperature measurements are practically excluded and that the thermoelement is not sensitive to thermal shocks. The construction complexity in order to achieve this should be kept low, whilst nevertheless providing high measuring accuracy with a simple design.

[0009]To avoid damage during installation of the thermoelement due to excessively hard contact between a support leg and the corresponding component of the thermal process system and, in accordance with a different embodiment, there is provision for the holding tube arranged between the connection head and the support leg to be divided into two sections, and for a coil compression spring disposed between the two sections such that the coil compression spring is supported against the sections, in which case the end areas of the coil compression spring is firmly connected to the two sections, preferably by means of crimping.

[0012]Furthermore, it is advantageous for the holding tube to be supported against the protective tube on the end facing the connection head in a torsionally rigid arrangement. The holding tube is therefore provided with a partially open flange with one or more grooves into which the protective tube engages with an axially projecting shoulder for each groove located in the outer edge area.

[0013]Due to this embodiment, the protective tube and / or the holding tube can be made from a gas-tight, heat resistant material, preferably, of silicon carbide, with the effect that it is insensitive to thermal shock.

[0014]If a thermoelement is configured in accordance with the present invention, the heat input into the connection head via the holding tube is practically excluded although the holding tube can be manufactured from silicon carbide and, as a result, falsifications of the measuring results are to all intents and purposes ruled out. The thermally insulating arrangement of the protective tube in relation to the holding tube, as well as the thermally insulating attachment of the holding tube on the connection head ensures that the connection head is not influenced by conducted heat. Also, because the holding tube is supported on the protecting tube in a torsionally rigid arrangement and because it can be configured in sections, this provides for an operationally reliable construction, as well as installation of the thermoelement, without damage. Accordingly, with little complexity, a thermoelement is created which permits accurate measurements of temperature to be taken over long periods even in excess of 1200° C., without susceptibility to thermal shocks, for example in mobile measuring positions.

Problems solved by technology

This results in impairments and therefore inaccuracies in the measuring result, with the effect that incorrect temperature data must be accepted.

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